There are numerous circumstances, particularly in vehicle and appliance construction, where it is desirable to attach an element, such as a bundle of electrical wires or tubing to the near side of a thin wall. Frequently the far side of the thin wall is not easily accessible and it is therefore desirable to allow attachment exclusively with activity on the near side of the wall. The present invention concerns a solution to this problem in which a small aperture is formed in the thin wall, and an arrowhead connector is easily pushed through the aperture but is removed from the aperture only with extreme difficulty. By connecting this arrowhead connector to a cable tie of the conventional type, a very effective system for connecting elements such as electrical cable to a sheet metal wall can result. Furthermore, this type of connector allows nondestructive replacement since the connector is designed to be disengaged from the aperture without damage to the aperture.
When this system is used on products such as vehicles which are exposed to extremes of temperature and moisture and are exposed to the ravages of time, connectors of the prior art type, which are typically formed of engineering polymers, can fail in their function in various ways and, as a result, the elements which are intended to be connected and essentially immobilized are allowed to break loose, rattle and cause various disturbances which are unacceptable to the operator of the vehicle and which require expensive and inconvenient maintenance.
A particular source of failure concerns the design of the arrow connector and the means by which it connects to the cable tie.
The prior art approaches to this arrowhead connector generally take two forms. The basic form is a unitary arrowhead mounted on the end of a unitary support which is connected to the cable tie. This design is shown in FIGS. 14-16. Those familiar with the drawability requirements of high speed injection molding of plastic will recognize that this design inherently includes certain limitations which, when applied to the present application, frequently result in service failures. The concept of drawability refers to the property of a molded workpiece that the two halves of the mold can be drawn apart and opened without the completed workpiece interfering with that motion. It usually means (that is, in a mold without side action) that there are one or more closed parting lines on the workpiece which separate the surface that faces one mold half from the surface that faces the other half, and no point faces a mold half through another part of the workpiece. More specifically, if the unitary support does not have a large cross-sectional area, it tends to break off at the point where it is connected to the cable tie. However, if the support does have a large cross-sectional area, it creates a rigid connection at its arrow end and causes the insertion force of the arrow to be unacceptably high. On the other hand, if the arrow end of the support is made very small, the connection between the support and the arrow head will fail. Because of drawability considerations, it is essentially impossible, at reasonable cost, to make the support large at the bottom and small at the top even if the above considerations would allow the resulting structure to be acceptable in the service environment. As a result, the wings or blades of the arrowhead are required to be both flexible, to allow insertion, and strong, to prevent unintended extraction. This conflict in properties often results in failure of the connector.
A second approach, which was an attempt to overcome the above-described disadvantages of the unitary-arrow, unitary-support design, involved a split arrowhead. In that design, shown in FIGS. 17-21, the support was actually split into two arms and each of the arms carried one of the blades of the split arrowhead. The resulting structure was an improvement over the unitary head design but continued to experience an unacceptable level of service failures. The service failures basically concentrated around two areas. One area involved failures at the location where the support connected to the tie. The other problem involved essentially a false connection. Frequently, the application of the system caused the arrow to be inserted into the aperture at an angle. See FIG. 20. If both of the blades or wings of the arrowhead did not enter the aperture, but rather if only one of the blades entered the aperture, frequently that blade could catch on the far surface of the wall and create an apparent connection. See FIG. 21. Because the remaining blade would be pressed snugly against the near wall, the resulting structure appeared and felt quite solid. However, after a short time, the vibration associated with the service environment would cause the connector to pull out and would result in a failure. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.
It is, therefore, an outstanding object of the invention to provide a locator tie which can easily be connected to the element which is to be located.
Another object of this invention is the provision of a locator tie which can easily be connected through an aperture in a thin wall.
A further object of the present invention is the provision of a locator tie which has a very low insertion force when it is being inserted into the aperture of a wall.
It is another object of the instant invention to provide a locator tie which has a very high extraction force once it has been inserted into an aperture in a wall.
A still further object of the invention is the provision of an arrowhead support structure which is drawable from molding cavities and yet has reinforcements and strain relief at points of potential failure.
A still further object of the present invention is the provision of an arrowhead support structure which is relatively uniform along its length in peripheral dimension but which has a low compression resistance at its arrow end and a very large surface area at its tie end.
Another object of the invention is the provision of a locator tie which is easy and inexpensive to manufacture, easy and inexpensive to apply and which is capable of a long and useful life with minimum maintenance.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.